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DEPARTMENT OF COMMERCEWASHINGTON

ELIMINATION OF WASTE SERIES

RECOMMENDED MINIMUM

REQUIREMENTS FOR MASONRY WALL

CONSTRUCTION

REPORTOF

BUILDING CODE COMMITTEE

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BUREAU OF STANDARDS

WASHINGTONGOVERNMENT PRINTING OFFICE

1925

UNITED STATES DEPARTMENT OF COMMERCEHERBERT HOOVER, SECRETARY

ELIMINATION OF WASTE SERIES

RECOMMENDED MINIMUM

REQUIREMENTS FOR MASONRY WALL

CONSTRUCTION

REPORT OFBUILDING CODE COMMITTEE

JUNE 28, 1924

IRA H. WOOLSON, ChairmanEDWIN H. BROWNWILLIAM K. HATTALBERT KAHN

RUDOLPH P. MILLERJOHN A. NEWLINJOSEPH R. WORCESTER

FRANK P. CARTWRIGHT, Technical Secretary

JOHN M. GRIES, Chief, Division of Building and Housing

BUREAU OF STANDARDS

PRICE, 15 CENTSSold only by the Superintendent of Documents, Government Printing Office

Washington, D. C.

WASHINGTONGOVERNMENT PRINTING OFFICE

1925

MEMBERSHIP OF THE BUILDING CODE COMMITTEEOF THE DEPARTMENT OF COMMERCE

Ira H. Woolson, consulting engineer National Board of Fire Un-derwriters, New York, N. Y., chairman

;member American Society

of Mechanical Engineers, American Society for Testing Materials,National Fire Protection Association, American Concrete Institute.

Edwin H. Brown, architect, Minneapolis, Minn.; secretary Ameri-can Institute of Architects.

William K. Hatt, professor of civil engineering, Purdue Univer-sity; member American Society of Civil Engineers; AmericanConcrete Institute.

Albert Kahn, architect, Detroit, Mich.;fellow American Institute

of Architects.

Rudolph P. Miller, consulting enginer, New York, N. Y.;presi-

dent Building Officials Conference; ex-superintendent of build-

ings, New York, N. Y.;member American Institute of Consulting

Engineers, American Society of Civil Engineers, American Societyfor Testing Materials.

John A. Newlin, in charge of section of timber mechanics ForestProducts Laboratory, Forest Service, United States Department

of Agriculture, Madison, Wis.;member American Society for

Testing Materials, American Society of Civil Engineers, associate

member American Railway Engineering Association.

Joseph R. Worcester, consulting engineer, Boston, Mass.; memberAmerican Society of Civil Engineers, American Institute of Con-

sulting Engineers.

Frank P. Cartwright, technical secretary.

ii

CONTENTS

PART I.—INTRODUCTIONPage

Acknowledgment of assistance 2Scope of report . 3

PART II.—RECOMMENDED MINIMUM REQUIREMENTS FOR MASONRYWALL CONSTRUCTION

Article I.—Definitions 4Sec. 1. Definitions 4

Article II.—Solid brick walls 5Sec. 2. Quality of materials 5

Sec. 3. Lateral support i 6

Sec. 4. Working stresses 6Sec. 5. Thickness of exterior walls 7

Sec. 6. Bond 8Sec. 7. Piers ' 8

Sec. 8. Chases and recesses ; arches and lintels^ 9Article III.—Walls of hollow tile, concrete block or tile, and hollow walls

of brick 9

Sec. 9. Quality of materials 9Sec. 10. Lateral support 10

Sec. 11. Working stresses 10Sec. 12. Thickness and height of exterior walls 10Sec. 13. Bond ; 11Sec. 14. Beam supports ., 11Sec. 15. Piers 11

Sec. 16. Chases and recesses ; arches and lintels 11Article IV.—Walls of plain concrete 12

Sec. 17. Concrete materials 12

Sec. 18. Lateral support 12

Sec. 19. Working stresses 13Sec. 20. Thickness of walls 13

Sec. 21. Reinforcement 14

Sec. 22. Piers __ 14

Sec. 23. Chases and recesses 14Article V.—Stonewalls . — 14

Sec. 24. Working stresses 14Sec. 25. Lateral support and thickness 14Sec. 26. Bond 15Sec. 27. Chases and recesses 15

Article VI.—Veneered walls 15Sec. 28. Quality of materials 15

Sec. 29. Working stresses 15Sec. 30. Attachment of veneering 15

Sec. 31. Height of veneered walls 15

in

IV CONTENTS

PageArticle VII.—Faced walls ! 15

Sec. 32. Quality of materials 15

Sec. 33. Working stresses 16Sec. 34. Thickness 16

Sec. 35. Bond Sj 16Article VIII.—Fire walls and fire division walls and partitions 16

Sec. 36. Brick and plain concrete fire walls 16Sec. 37. Fire walls of hollow tile, concrete block or concrete tile, or

of hollow wall construction 17

Sec. 38. Fire division walls 17

Sec. 39. Alternate requirements for fire and fire division walls 17Sec. 40. Parapet walls 18Sec. 41. Bearing partitions 18

Sec. 42. Nonbearing partitions : 18Article IX.—Foundation walls— . 18

Sec. 43. Foundation walls 18Article X.—Skeleton construction 19

Sec. 44. Panel and inclosure walls ^Article XI.—New types of masonry construction 19

Sec. 45. New masonry construction 19Article XII.—Miscellaneous requirements 20

Sec. 46. Anchoring walls 20

Sec. 47. Use of existing walls j 2®Sec. 48. Corbeling of chimneys 20

Sec. 49. Cornices 20

PART III.—APPENDIX

Par. 1. Purpose;

21

Par. 2. Justification for requirements, and influence of building inspec-

tion 21

Par. 3. Status of the committee’s recommendations 22

Par. 4. Function of walls 23

Par. 5. Variation in code requirements 23

Par. 6. Walls in skeleton construction 25

Par. 7. Fire and fire division walls 26

Par. 8. Concrete considered as masonry 28

Par. 9. Quality of brick 28

Par. 10. Mortar materials 30

Par. 11. Tests of compressive strength of brick masonry 31

Par. 12. Lateral support of walls 12^-———. 32

Par. 13. Elements affecting strength of brickwork 34

1. Strength of individual brick — 342. Mortar, materials, and proportions 36

3. Ratio of height to thickness 36

4. Bond and jointing 37

5. Workmanship — 376. Age of masonry I --- 38

7. Manner of loading —— 38Par. 14. Factors of safety for brickwork 38

Par. 15. Stresses in brickwork , k—JO 39Par. 16. Thickness of brick walls -- — 41Par. 17. Heat transmission of masonry walls 42

CONTENTS V

Page

Par. 18. Factors affecting stability of walls 44

1. Foundation conditions 44

2. Vibration 44

3. Height and width of buildings 444. Methods of anchorage ' 44

5. Rigidity of floors 44

6. Influence of span 45

7. Fire exposure 45

8. Wind pressure—— 459. Percentage and arrangement of openings in walls 45

Par. 19. Bond for hrick walls 45Par. 20. Height of brick piers 46

Par. 21. Height of masonry walls . 46Par. 22. Lining existing walls . 46

Par. 23. Lintels 46

Par. 24. Quality of hollow tile and concrete block or concrete tile 46Par. 25. Working stresses for hollow walls 48Par. 26. Support for slabs, beams, and girders 49Par. 27. Concrete walls—solid and hollow 49Par. 28. Walls and piers of stone masonry.Par. 29. Parapet walls

Par. 30. Foundation walls

Par. 31. New masonry constructionPar. 32. Anchorage of walls : 51Par. 33. Professional assistance rendered 52

Par. 34. Bibliography 52

FIGURES

1. Desirable methods of bonding brick walls of various thicknessesand types

;—||| 2 82. Compression test of 8-inch solid wall of brick. Note failure due to

breakage of headers. Bureau of Standards,Washington, D. C_ Facing 443. Compression test of 8-inch hollow wall of brick. Bureau of Stand-

ards, Washington, D. C ! Facing 454. Compression test of large brick pier in 10,000,000-pound machine.

Bureau of Standards laboratory at Pittsburg Facing 46

gg

§§

LETTER OF SUBMITTAL

Washington, October 1,192If..

Hon. Herbert Hoover,Secretary of Commerce, Washington, D. C.

Dear Sir : Under instruction from the Building Code Committee,appointed by you for the purpose of standardizing and simplifyingbuilding laws, I have the honor to submit herewith a report cover-

ing Recommended Minimum Requirements for Masonry Wall Con-struction. If this report meets with your approval, the committee

recommends that it be printed for public distribution.The same plan followed in preparing the committee’s report

on small dwelling construction was employed in drafting this re-port, namely, to collect data, prepare a tentative report, solicit

cooperative criticism from every available source, and then draft

a final report based upon the weight of accumulated opinion, bal-anced by the committee’s best judgment. The details of this pro-cedure are described in the introduction. The committee believesthat an application of its recommendations in building code practice

will result in material reduction in building costs without impair-

ment of safety or permanency.In this report, as in our first report, the Appendix forms a major

portion of the publication. It contains a digest of data used as a

basis for the requirements of Part II and considerable other matter

of an educational character. The committee is confident that, al-though this material is not adapted for inclusion in a building

ordinance, except in an appendix, it is nevertheless a very impor-

tant part of the report and should be recognized as such.

Yours very truly,Ira H. Woolson,

Chairman Building Code Committee,

Department of Commerce.VI

LETTER OF ACCEPTANCE

Department of Commerce,Office of the Secretary,Washington, October 23, 1924-.

Mr. Ira H. Woolson,Chairman Building Code Committee

,

Department of Commerce , Washington, D. C.Dear Mr. Woolson : I have received with great satisfaction the

Recommended Minimum Requirements for Masonry Wall Construc-tion, prepared by the Building Code Committee.

This report I know represents a great deal of painstaking laboron the part of yourself and the other members of the committee.Your work has been especially valuable, since it was on problemsthat would otherwise have remained without comprehensive, sys-

tematic efforts at solution. This has been accomplished by further

cooperation between the Government and the public. The recom-mendations are of great importance from the point of view of elimi-nation of waste, and should result in greater returns to the public

for money spent on construction.I have no hesitation in thanking you all in behalf of the American

public, and I hope that the advantages of your recommendations

will be quickly availed of by our municipalities, and the construc-tion industries generally.

Yours faithfully,

Herbert Hoover.

RECOMMENDED MINIMUM REQUIREMENTS FOR MASONRY

WALL CONSTRUCTION

Report of the Building Code Committee of the

Department of Commerce

This report is divided into three general headings, as follows

:

Part I.

—

Introduction:

Describes briefly the organization of the committee and its method

in preparing and presenting the recommendations.

Part II.

—

Minimxim requirements for safe and economical construc-

tion of masonry walls

:

These are briefly stated in the form of recommendations suitable

for State or municipal adoption.

Part III.

—

Appendix:Contains material not suited for incorporation in a building law,

but which is explanatory of the requirements recommended in Part

II and descriptive of good practice.

PART I.—INTRODUCTION

Several independent analyses have indicated forcefully that pres-

ent municipal code requirements for masonry wall construction are,

in general, unnecessarily restrictive of building enterprise, often re-

quire uneconomical construction, and are lacking in the uniformity

desirable for convenience of designers and builders. The follow-ing report summarizes some of these analyses, describes investiga-

tions of the factors affecting masonry wall essentials, and presents

recommendations for uniform code practice.

The building code committee of the Department of Commercewas organized early in 1921, in response to a generally expressed

public demand for greater uniformity and economy in building coderequirements. Its first work concerned regulations affecting con-struction of small dwellings and the final report on that subject waspublished in January, 1923.1

1 Recommended Minimum Requirements for Small Dwelling Construction; a. 100-pagereport obtainable from the Superintendent of Documents, Government Printing Office,Washington, D. C., at 15 cents per copy.

28934°—25 2 1

2 RECOMMENDED MINIMUM REQUIREMENTS

Following its organization the committee made an extensivecanvass of professional opinion as to what parts of building codesmost urgently needed revision and standardization. This showedthat masonry wall regulations differ widely in various cities; thatallowable masonry stresses and fire resistance requirements are basedon inadequate knowledge of service under loading and fire exposure

;

and that as a result there is lack of safety in some localities andunnecessary use of materials and labor in others.

It was decided to collect all reliable data available for guidanceof those drafting masonry wall provisions and to prepare recom-mendations representing the best information obtainable on the sub-

ject. An investigation of fire resistance of masonry walls had beeninstituted at the Bureau of Standards and has since been completed,and the results made available for this committee. Tests were madeupon solid and hollow brick walls 11 by 16 feet in area and builtwith different varieties of brick and mortar. In the meantime allavailable data on the compressive strength of masonry were corre-lated, with especial care to evaluate the effects of differing conditions

on strength and stability. These include results from an elaborateinvestigation of the compressive strength of brick walls in the larg-

est units adapted to the 10,000,000-pound testing machine at the

Bureau of Standards’ former Pittsburgh laboratory. The advice ofmany experienced masonry builders was also obtained.With this information in hand the committee prepared a tenta-

tive draft of code requirements regulating masonry wall construc-

tion in all types of buildings, together with an appendix explanatory

of these requirements and including certain valuable material which

had resulted from the investigations mentioned. Over 800 copies of

this draft in mimeographed form, were submitted to architects, engi-

neers, building officials, contractors, insurance adjusters, and others,

whose experience and interest qualified them to discuss the subjectwith authority.

The tentative draft was thoroughly reviewed. Over 150 letterswere received presenting the well-considered opinions of about 200

experienced observers. These were summarized in form for ready

reference and several meetings of the committee held for their con-

sideration in connection with preparation of this report.

SCOPE OF REPORT

This report deals with exterior and interior masonry walls for all

buildings. Walls for small dwellings are included, but are treated

more specifically in the report on Recommended Minimum Require-ments for Small Dwelling Construction, previously mentioned.

Note.

—

For reasons given in the Appendix, paragraph 8-3, reinforced con-

crete walls have been omitted.

MASONRY WALL CONSTRUCTION 3

ACKNOWLEDGMENT OF ASSISTANCE

The committee desires to express its appreciation of the coopera-tion extended by Bureau of Standards officials. S. H. Ingberg, of

the bureau staff, rendered valuable assistance by compiling data,making available results of fire tests, by working with the committee

at several meetings, and by supplying a discussion ,of bendingstresses in walls due to wind loads and floor reactions. Theunequaled research facilities of the bureau have been freely

employed, and the results of numerous investigations made by thebureau in the field of masonry construction have been most helpful.

The committee also acknowledges the invaluable cooperationreceived from the great number of architects, engineers, buildinginspectors, fire chiefs, and others with whom it has been in contact.Their prompt and well-considered response to requests for informa-

tion has greatly facilitated the work and has been much appreciated.It has been impracticable to report to each commentator the dispo-

sition of his suggestions. Many of the more important questionsraised have been discussed in the Appendix.

PART II.—RECOMMENDED MINIMUM REQUIREMENTSFOR MASONRY WALL CONSTRUCTION

ARTICLE I.—DEFINITIONS

Section 1. Definitions.

—

For the purposes of this code the termshere defined shall have the following meanings.

1. Bearing wall.—A wall which supports any vertical load inaddition to its own weight.

2. Nonbearing wall.—A wall which supports no load other thanits own weight.

3. Panel wall.—A nonbearing wall in skeleton construction, builtbetween columns or piers and wholly supported at each story. (See

Appendix, par. 6-1.)

4. Inclosure wall.—An exterior nonbearing wall in skeleton con-struction anchored to columns, piers, or floors, but not necessarily

built between columns or piers. (See Appendix, par. 6-2.)

5. Curtain wall.—A nonbearing wall between columns or piers andwhich is not supported by girders or beams.

6. Party wall.—A wall used or adapted for joint service be-tween two buildings.

7. Fire wall.—A wall which subdivides a building to restrict thespread of fire, by starting at the foundation and extending con-

tinuously through all stories to and above the roof. (See Appendix,

par. 7.)

8. Fire division wall.—A wall which subdivides a fire resistivebuilding to restrict the spread of fire, but is not necessarily continu-

ous through all stories nor extended through the roof. (See Ap-pendix, pars. 7 and 17.)

9. Veneered wall.—A wall having a masonry facing which is notattached and bonded to the backing so as to form an integral part

of the wall for purposes of load bearing and stability.10. Faced wall.—A wall in which the masonry facing and back-

ing are so bonded as to exert common action under load.11. Masonry.—Stone, brick, concrete, hollow tile, concrete block or

tile, gypsum block, or other similar building units or materials or acombination of same, bonded together with mortar to form a wall,pier, or buttress. (See Appendix, par. 8.)

12. Piers.—All bearing walls having a horizontal cross section of4 square feet or less and not bonded at the sides into associated

masonry shall be considered as piers.13. Portland cement mortar.—A mortar composed of 1 part Port-

land cement to not more than 3 parts of sand, proportioned byvolume, with an allowable addition of hydrated lime not to exceed

4 /


15 per cent of the cement by volume. (See Appendix, par. 10-4;

and 13-2.)14. Cement-lime mortar.—A mortar composed of 1 part Portland

cement, 1 part hydrated lime, and not more than 6 parts of sand,proportioned by volume.

15. Lime mortar.—A mortar composed of 1 part slaked lime (limeputty) or dry hydrated lime and not more than 4 parts of sand, pro-portioned by volume. (See Appendix, par. 13-2.)

16. Natural cement mortar.—A mortar composed of 1 part naturalcement to not more than 3 parts of sand, proportioned by volume.

17. Ashlar masonry.—Masonry of sawed, dressed, tooled, orquarry-faced stone with proper bond.

18. Ashlar facing.—Sawed or dressed squared stones used in facingmasonry walls.

19. Random ashlar facing.—Sawed or dressed squared stone ofvarious sizes properly bonded or fitted with close joints used for the

facing of masonry walls.20. Coursed rubble.—Masonry composed of roughly shaped stones

fitting approximately on level beds and well bonded.

21. Random rubble.—Masonry composed*of roughly shaped stonelaid without regularity of coursing, but fitting together to form

well-defined joints.

22. Rough or ordinary rubble.—Masonry composed of unsquaredor field stones laid without regularity of coursing.

23. Rubble concrete.—Portland cement concrete in which the finermaterials form a matrix for large stones and bowlders, sometimestermed cyclopean concrete.

Notes.—1. Unless otherwise stated the word “ concrete ” for the purposesof this code is understood to mean Portland cement concrete.

2. Unless otherwise stated units of materials other than burned clay, having

the same general shape and size of brick, are for the purposes of this codeconsidered as brick. (See Appendix, par. 9-1.)

3. Unless otherwise stated the term “ hollow tile ” used without a qualifying

adjective, is understood to mean clay hollow tile.

ARTICLE II.—SOLID BRICK WALLS

Sec. 2. Quality of materials.—Brick, and sand-lime brick, usedfor bearing walls or piers shall be of quality at least equal to the“ medium brick ” described by the Standard Specifications for Build-ing Brick of the American Society for Testing Materials, except thatwhen the average compressive strength of brick grading “ soft ” bythe absorption test, is more than 2,500 pounds per square inch, therequirements as to absorption may be waived. When used for non-bearing purposes and not exposed to the weather, brick may be ofquality not inferior in any respect to the “ soft ” brick described in

the above specifications. (See Appendix, pars. 9-2 and -3.)


The average compressive strength of concrete brick 28 days afterbeing manufactured or when delivered on the job, shall be not lessthan 1,500 pounds per square inch of gross cross-sectional area testedin the position as laid in the wall, and the compressive strength ofany individual brick thus tested shall be not less than 1,000 poundsper square inch. (See Appendix, par. 9-4.)

Concrete brick subjected to a 24-hour immersion test shall absorb

not more than 12 per cent of their dry weight, except that for suchbrick weighing less than 125 pounds per cubic foot the average ab-sorption in per cent by weight shall be not more than 12 multiplied'by 125 and divided by the unit weight in pounds per cubic foot ofthe concrete under consideration. (See Appendix, par. 9-5.)

All cements and limes used in mortar shall conform to the require-ments of the standard specifications for these materials issued by theAmerican Society for Testing Materials. (See Appendix, par.10-2.)

Sand used in mortar shall be clean and free from animal or vege-table matter. (See Appendix, par. 10-1.) (For precautions neces-sary in laying brickwork in freezing weather or in warm dryweather see Appendix, par. 13-5.)

Sec. 3. Lateral Support.—Solid brick walls shall be supportedat right angles to the wall face at intervals not exceeding eight-

een times the wall thickness in the top story or twenty times

the wall thickness elsewhere. Such lateral support may be obtainedby cross walls, piers, or buttresses, when the limiting distance ismeasured horizontally, or by floors when the limiting distance ismeasured vertically. Sufficient bonding or anchorage shall be pro-

vided between the wall and the supports to resist the assumed vfind

force, acting in an outward direction. Piers or buttresses relied upon

for lateral support shall have sufficient strength and stability to

transfer the wind force, acting in either direction to the ground.

When walls are dependent upon floors for their lateral support,provision shall be made in the building to transfer the lateral forces

resisted by all floors to the ground. (See Appendix, par. 12.)

'

Sec. 4. Working Stresses.—The maximum allowable compressivestresses in brick masonry due to combined live and dead loads shall

not exceed the following limits. (See Appendix, par. 9-2.)

Brick masonry stresses

Maximum unit working stresses(pounds per square inch)

Unit Portlandcementmortar

Naturalcement orcement-limemortar

Limemortar

Brick (clay) medium grade 170 130 90Sand-lime brick 170 130 90

Concrete br c 170 130 70'


Where the effects of eccentric loading and lateral forces are fullyanalyzed and allowance made for them in the design, or under localconcentrated loads applied to a limited proportion of the total area

of the wall, the working stresses in this table may be increased by50 per cent. (See Appendix, par. 15.)

Note.—See Appendix, paragraphs 13 and 14, respectively, for effect of dif-ferent factors on strength and stability of masonry.

Sec. 5.—Thickness or Exterior Walls Other Than in Skele-ton Construction. 2—-The thickness of solid brick bearing wallsshall be sufficient at all points to keep the combined stresses due tolive and dead loads for which the building is designed within thelimits prescribed by section 4. (See Appendix, par. 15.)The minimum thickness for solid brick exterior bearing or party

walls shall be 12 inches for the uppermost 35 feet of their height,and shall be increased 4 inches for each successive 35 feet or frac-tion thereof measured downward from the top of the wall

;except

that the top story exterior bearing wall of a building not exceeding

three stories or 40 feet in height, or the wall of a one-story commer-cial or industrial building may be 8 inches thick, provided that such8-inch wall does not exceed 12 feet unsupported height and that theroof beams are horizontal; and except that exterior solid brick bear-ing walls of one and two family dwellings may be 8 inches thickwhen not more than 30 feet in height. When gable construction isused for such dwellings, an additional 5 feet is permitted to the peak

of the gable. (See Appendix, par. 16.)Where solid brick exterior bearing or party walls are stiffened at

distances not greater than 12 feet apart by cross walls, or by internalor external offsets or returns, at least 2 feet deep, they may be 12inches thick for the uppermost 70 feet, measured downward fromthe top of the wall, and shall be increased 4 inches in thickness for

each successive 70 feet or fraction thereof.

Note.—

S

ee Appendix, paragraphs 2-2 and 13-5 for influence of workman-

ship ; paragraph 21, for discussion of wall heights. See Part II, section 3, and

Appendix, paragraph 12, for lateral support of walls.

The minimum thickness of solid brick exterior nonbearing wallsshall be 12 inches for the uppermost 70 feet of their height, and

shall be increased 4 inches for each successive 35 feet or fraction

thereof, measured downward from the top of the wall, except thatthe top story wall of a building not exceeding three stories or 40

feet in height, or the wall of a one-story commercial or industrial

building may be 8 inches thick, provided that such 8-inch wall doesnot exceed 12 feet unsupported height, and that the roof beams are

2 For thickness requirements for walls in skeleton constructed buildings, see Part II,sec. 44. For discussion on allowable percentage of openings, see Appendix, par. 18-9.

zo


horizontal;and except that solid brick nonbearing walls of one and

two family dwellings may be 8 inches thick when not more than 30feet in height. Whengable construction is used

for such dwellings an addi-tional 5 feet is permitted tothe peak of the gable. (SeeAppendix, pars. 16 and 18.For interior wall require-ments, see Part II, secs. 36to 39, also 41 and 42.)

Sec. 6. Bond.

—

In allbrick walls at least every

sixth course on both sidesof the wall shall be a

header course or there

shall be at least one full

length header in every 72

square inches of each wall

surface. In walls morethan 12 inches thick the

inner joints of header

courses shall be covered

with another headercourse which shall breakjoints with the course

below. (See fig. 1 andAppendix, par. 19.)Where running bond is

used, every sixth course

on each face shall be

bonded into the back-

ing by cutting the face

brick course and using

diagonal headers behind it

or by using a split brick.

Note.—For requirements ap-plying to veneered walls, see

Part II, Article VI.

Sec. 7. Piers.

—

The un-supported height of piers

shall not exceed ten times

their least dimension.(See Appendix, par. 20.)

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Sec. 8. Chases and Eecesses.—There shall be no chases in 8-inchwalls or within the required area of any pier, and no chase in any

wall or pier shall be deeper than one-third the wall thickness.

No horizontal chase shall exceed 4 feet in length, nor shall thehorizontal projection of any diagonal chase exceed 4 feet.

Eecesses for stairways or elevators may be left in walls, but inno case shall the walls at such points be less than the required

thickness of walls of the fourth story above the ground floorunless reinforced by additional piers, by steel or reinforcedconcrete girders, or steel or reinforced concrete columns and girders,

securely anchored to the walls on each side of such recesses. Ee-

cesses for alcoves and similar purposes shall have not less than 8

inches of material at the back. Such recesses shall be not morethan 8 feet in width and shall be arched over or spanned with lintels.

The aggregate area of recesses and chases in any wall shall notexceed one-fourth the whole area of the face of the wall in any

story.

No chases or recesses shall be permitted in fire or fire divisionwalls that will reduce the thickness below the minimum specified inthis code. (See Part II, secs. 86 to 39.)

Openings for doors and windows shall have well-buttressed arches

or lintels of masonry, or of metal with bearing at each end of not

less than 4 inches on the wall. On the inside of openings less than 4feet wide, in which the thickness of arches and lintels is less than that

of the wall supported, timber may be used, which will rest at eachend not more than 2 inches on the wall and be chamfered or cut to

serve as arch centers. (See Appendix, par. 18-4, and par. 32 for

discussion of anchorage.)

ARTICLE III.—WALLS OF HOLLOW TILE, CONCRETE BLOCK ORTILE, AND HOLLOW WALLS OF BRICK

Sec. 9. Quality of Materials.—Hollow tile.—Hollow tile used forexterior bearing walls or piers or for party walls shall be of quality

at least equal to the “ medium class ” as prescribed by the TentativeSpecifications for Hollow Burned-Clay Load-Bearing Wall Tile of

the American Society for Testing Materials. (See Appendix, par.24-1 and -2.)

When used for nonbearing purposes and not exposed to theweather, hollow tile may be of quality not inferior in any respect tothe “ soft class ” described in the above specifications.

Note.

—

For quality of tile used in partitions, see Part II, sections 41 and 42.

Concrete block or concrete tile .—The average compressive strengthof concrete block or tile used for exterior or party walls or piers

shall be not less than 700 pounds per square inch of gross sectional

area tested in position as used in the wall. The absorption of con-

289340—25—

3

10 RECOMMENDED MINIMUM REQUIREMENTS'

Crete block or tile shall not exceed 10 per cent under a 24-hour im-

mersion test, except that where concrete block or tile have an averagecompressive strength of over 1,200 pounds per square inch grossarea, or where they are not exposed to dampness, or where they arecoated with stucco, the requirement as to absorption may be waived.For block or tile made of concrete weighing less than 140 pounds percubic foot, the average absorption in per cent by weight shall be notmore than 10 multiplied by 140 and divided by the unit weight inpounds per cubic foot of the concrete under consideration. (SeeAppendix, par. 9-5.)

Tests on concrete block shall be conducted in accordance with the

Standard Specifications of the American Concrete Institute. (SeeAppendix, par. 24-3.)

Brick.—Brick for hollow walls shall conform to requirements ofPart II, section 2.

Mortar.—Either Portland cement mortar as defined in section 1,or a special cement-lime mortar mixed in proportions of 1 partPortland cement, 1 part slaked lime (lime putty) or dry hydrated

lime, and not more than 4 parts sand, shall be used for walls of

hollow unit construction or hollow walls of brick.

Sec. 10. Lateral Support.—Walls of hollow tile or of concreteblock or tile, and all hollow walls of brick shall be supported atright angles to the wall face at intervals not exceeding sixteen times

the wall thickness in top stories, or eighteen times the wall thickness

elsewhere. Such lateral support may be in the form of cross walls,piers, or buttresses when the limiting distance is horizontal, or byfloors when the limiting distance is vertical. Sufficient bonding oranchorage shall be provided between the wall and the supports to

resist the assumed wind force acting in an outward direction. Piers

or buttresses relied upon for lateral support shall have sufficient

strength and stability to transmit the wind force, acting in either

direction, to the ground. When walls are dependent on floors fortheir lateral support provision shall be made in the building totransfer the lateral force resisted by all floors to the ground. (See

Appendix, par. 12.)

Sec. 11. Working Stresses.—The maximum allowable compres-sive stresses in masonry of hollow tile, concrete block or concrete

tile, or hollow walls of brick, due to combined live and dead loads,

shall not exceed 80 pounds per square inch of gross sectional area,

when laid with Portland cement mortar, and 70 pounds per square

inch of gross sectional area when laid with special cement-lime

mortar. (See section 9, Mortar. See also Appendix, par. 25-1.)Sec. 12. Thickness and Height of Exterior Walls Other Than

in Skeleton Construction. 3—Walls of hollow tile, concrete block or3 For thickness requirements for walls in skeleton constructed buildings, see Part II,

sec. 44. For discussion on allowable percentage of openings, see Appendix, par. 18-9.


tile, or hollow walls of brick shall not exceed 50 feet in height above

the top of foundation walls.

The thickness of walls of the above materials and types shall besufficient at all points to keep the stresses due to combined live and

dead loads for which the building is designed within the limits pre-

scribed by section 11.The minimum thickness of exterior walls of hollow tile, or con-

crete block or tile, or of hollow-wall construction shall be 12 inches

for the uppermost 35 feet of their height, and at least 16 inches

for the remaining lower portion; except that the top story wall

of a building not exceeding three stories or 40 feet in height, or the

wall of a one-story commercial or industrial building may be 8inches thick, provided that the roof beams are horizontal; and

except that exterior walls of one and two family dwellings maybe 8 inches thick for the uppermost 20 feet. When gable construc-tion is used for such dwellings an additional 5 feet is permitted to

the peak of the gable. (See Appendix, par. 16-6.)

Where walls are stiffened at distances not greater than 12 feetby cross walls or by internal or external returns at least 2 feetdeep, the thickness may be 12 inches throughout, except that thetop story, or for one and two family dwellings the uppermost 20 feet,may be 8 inches as previously provided. (See Appendix, par. 16-1and -4. For interior wall requirements see Part II, secs. 36 to 39,also 41 and 42.)

Sec. 13. Bond.

—

-Where two or more hollow units are used tomake up the thickness of a wall, the inner and outer courses shallbe bonded at vertical intervals not exceeding three courses by lappingat least one cell completely over a cell of the unit below.

Sec. 14. Beam Supports.

—

Suitable provision shall be made ateach line of floor beams in hollow walls or walls of hollow units,to shut off the spaces above from those below, and to ensure goodbearing for beams and uniform distribution of loads. (See Appen-dix, par. 26.)

Sec. 15. Piers.—Hollow tile or hollow concrete block or tile shallnot be used for isolated piers unless solidly filled with concrete. Theunsupported height of such piers shall not exceed 10 times their

least horizontal dimension. (See sec. 1, definition 12, and Appen-dix, par. 26.)

Sec. 16. Chases and Recesses.—Chases and recesses in walls ofhollow tile, hollow concrete block or tile, or in hollow walls of

brick shall not exceed in extent those permitted for solid brick

walls under the same conditions. Chases and recesses shall not be

cut in walls of the above types, but may be built in. No chases


or recesses shall be permitted in fire walls that will reduce thethickness below the minimum specified in this code.

Openings for doors and windows shall have well-buttressed archesor lintels of masonry or metal with bearing at each end of not lessthan 4 inches on the wall. On the inside of openings less than 4feet wide, in which the thickness of arches and lintels is less thanthat of the wall supported, timber may be used, which will restat each end not more than 2 inches on the wall and be chamferedor cut to serve as arch centers.

ARTICLE IV.—WALLS OF PLAIN CONCRETE

Sec. 17. Concrete Materials.—Monolithic concrete constructioncontaining not more than two-tenths of 1 per' cent of reinforcementshall be classed as plain concrete.

Materials for bearing walls and piers of plain concrete shall bemixed in proportions of 1 part of Portland cement to not more than

3 parts of sand and 5 parts of coarse aggregate, by volume, or a mix-ture of fine and coarse aggregates giving an equivalent strength anddensity.

Coarse aggregate shall consist of crushed stone, gravel, or crushed

slag, 85 per cent of which is retained on a No. 4 screen, and shall begraded in size from small to large particles. The particles shall beclean, hard, durable, and free from deleterious material. (See Ap-pendix, par. 27.)

Cement for plain concrete shall conform to the requirements ofthe Standard Specifications and Tests for Portland Cement of theAmerican Society for Testing Materials.Fine aggregate shall consist of sand, washed stone screenings or

other similar inert materials, or a combination thereof, having clean,

hard, strong, durable uncoated grains and free from injuriousamounts of dust, lumps, soft or flaky particles, shale, alkali, organic

matter, loam or other deleterious substances; and shall range from

fine to coarse. Not less than 95 per cent shall pass a No. 4 sieve, andnot more than 30 per cent shall pass a No. 50 sieve, when testedaccording to standard practice prescribed by the American Society

for Testing Materials.

Sec. 18. Lateral Support.—Plain concrete walls shall be sup-ported at right angles to the wall face at intervals of not exceeding

twenty times the wall thickness. Such lateral support may be in theform of cross walls, piers, or buttresses when the limiting spacing ishorizontal, or by floors when the limiting distance is vertical. Suf-ficient bonding or anchorage shall be provided between the wall and

the supports to resist the assumed wind force acting in an outward

direction. Piers or buttresses relied upon for lateral support shall


have sufficient strength and stability to transfer the wind force, act-ing in either direction, to the ground. When walls are dependentupon floors for their lateral support provision shall be made in thebuilding to transfer the lateral force resisted by all floors to theground. (See Appendix, par. 12.)

Sec. 19. Working Stresses.—The maximum allowable stresses inmasonry of plain concrete of the proportions specified in section 17as a minimum due to combined dead and live loads shall not exceed400 pounds per square inch in compression, 35 pounds per square

inch in tension or diagonal tension;or 90 pounds per square inch in

punching shear. When plain concrete of greater strength is used theforegoing stresses may be increased to 20 per cent of the ultimatecompressive strength for concrete in compression, 2 per cent in ten-

sion or diagonal tension, and 4*4 per cent in punching shear.

Sec. 20. Thickness of Walls.

—

The minimum thickness of plainconcrete bearing walls shall be 10 inches for the uppermost 35 feet

of their height and shall be increased 4 inches for each successive 35

feet or fraction thereof, measured downward from the top of thewall, except that the top-story wall of a building not exceeding

three stories or 40 feet in height, or the wall of a one-story commer-

cial or industrial building may be 8 inches thick, provided that such8-inch wall does not exceed 12 feet unsupported height and that the

roof beams are horizontal, and except that exterior bearing walls of

one and two family dwellings may be 6 inches thick when not morethan 30 feet in height. When gable construction is used for suchdwellings an additional 5 feet is permitted to the peak of the gable.

(See Appendix, par. 16.)

When plain concrete bearing walls of buildings more than threestories high are stiffened at points not more than 12 feet apart bycross walls, or by internal or external offsets or returns at least 2 feet

deep, they may be 10 inches thick for the uppermost 70 feet of theirheight- and shall be increased 4 inches in thickness for each succes-

sive 70 feet or fraction thereof.

The minimum thickness of plain concrete exterior nonbearing wallsshall be 10 inches for the uppermost 70 feet of their height, and

shall be increased 4 inches for each successive 35 feet or fraction

thereof, measured downward from the top of the wall; except thatthe top story wall of a building not exceeding three stories or 40

feet in height, or the wall of a one-story commercial or industrial

building may be 8 inches thick, provided that such 8-inch wall doesnot exceed 12 feet unsupported height, and that the roof beams arehorizontal

;and except that exterior nonbearing walls of one and two

family dwellings may be 6 inches thick when not more than 30 feetin height. When gable construction is used for such dwellings an


additional 5 feet is permitted to the peak of the gable. (For dis-

cussion of heights, see Appendix, par. 21.)Hollow monolithic walls of plain concrete shall have the same net

cross sectional area of material, irrespective of the space within the

wall, as required for solid walls. The inner and outer parts of suchwalls shall be securely braced and tied together with noncorrodibleties or other means to bring them into common action. Where floorand roof systems are carried by such walls, provision shall be madefor the distribution of these loads to the full cross section of the wall.

(See Appendix, par. 27.) For interior wall requirements, see sec-tions 36 to 39, also 41 and 42.

Sec. 21. Reinforcement.—Reinforcement, not less than two-tenths of 1 per cent computed on a vertical height of 12 inches, shall

be placed over all wall openings and at corners of the structure to

prevent cracks. Floor and roof connection details shall be designed

to transmit safely the vertical and horizontal loads imposed.

Sec. 22. Piers.—The unsupported height of isolated piers of plainconcrete shall not exceed ten times their least dimension. (See sec.

1, definition 12.)

Sec. 23. Chases and Recesses.—Chases and recesses in plain con-crete walls shall not exceed in extent those permitted for solid brick

walls under the same conditions. (See Part II, sec. 8.)

article v.—stone walls

Sec. 24. Working Stresses.—The maximum allowable compressivestresses in rubble stonework due to combined live and dead loads

shall not exceed 140 pounds per square inch when laid in Portlandcement mortar, 100 pounds per square inch in natural cement or ce-

ment-lime mortar, and 70 pounds per square inch in lime mortar.

The maximum allowable compressive stress in ashlar masonry dueto combined live and dead loads shall not exceed the following limits

:

Maximum unit working stresses(pounds per square inch) laidin—

Unit

Portlandcementmortar

Cement-lime ornaturalcementmortar

Limemortar

Granite 800 640 400Limestone 500 400 250Marble 500 400 250Sandstone 400 320 160

Sec. 25. Lateral Support and Thickness.—Rubble stone wallsshall be 4 inches thicker than is required for solid brick walls of the

same respective heights, but in no part less than 16 inches.


The minimum thickness for walls or piers of ashlar masonryproperly bonded shall be the same as required for solid brick wallsand piers under similar conditions.

The lateral support for stone walls shall conform to the samerequirements specified for solid brick walls, Part II, section 3.

(For discussion of heights, see Appendix, par. 21.)Sec. 26. Bond.

—

Bond stones extending through the wall anduniformly distributed shall be provided to the extent of not less

than 10 per cent of the area, and there shall be at least one bondstone for every eight stretchers.

Sec. 27. Chases and Recesses.

—

Chases and recesses in stone wallsshall not exceed in extent those permitted for solid brick walls under

the same conditions. (See Part II, sec. 8.)

ARTICLE VI.—VENEERED WALLS

Sec. 28. Quality of Materials.

—

Materials used in the backing

and veneering of veneered walls shall conform in all respects to therequirements prescribed for such materials in Part II, sections 2, 9,and 17. Stone or architectural terra-cotta ashlar, or other approved

masonry material used for veneering, shall be not less than 3 inchesthick. In stone ashlar each stone shall have a reasonably uniform

thickness, but all stones need not necessarily be the same thickness.

Sec. 29. Working Stresses.

—

The maximum allowable compressivestresses on the backing of veneered walls, due to combined live and

dead loads, shall not exceed those elsewhere prescribed for masonry

of the type which forms such backing. In no case shall the veneer-

ing be considered a part of the wall in computing the strength ofbearing walls, nor shall it be considered a part of the required

thickness of the wall.

Sec. 30. Attachment of Veneering.—When walls are veneeredwith brick, terra cotta, stone or concrete trim stone the veneering

shall be tied into the backing either by a header for every 300

square inches of wall surface, or by substantial noncorrodible metal

wall ties spaced not farther apart than 1 foot vertically and 2 feet

horizontally. Headers shall project at least 3% inches into thebacking, and anchors shall be of substantial pattern. When veneer-ing is used special care shall be taken to fill all joints flujsh with!

mortar around wall openings. (See Appendix, par. 32-8.)

Sec. 31. Height of Veneered Walls.—Veneered walls shall notexceed 40 feet in height above foundations.

article vii.—faced walls

Sec. 32. Quality of Materials.—Materials used in the backingand facing of faced walls shall conform in all respects to the require-

ments prescribed for such materials in Part II, sections 2, 9, and 17.


Materials used for facing shall be not less than 3% inches thick, andin no case less in thickness than one-eighth the height of the unit,excepting that spandrel and other recessed panels, when approved,may be higher than eight times their thickness, provided they areof the minimum thickness required.

Sec. 33. Working Stresses,—The maximum allowable compres-sive stresses on faced walls due to combined live and dead loadsshall not exceed those elsewhere prescribed for masonry of the typewhich forms the backing. Where bonded to the backing as pro-vided in section 35 the full cross section of the facing may be con-sidered in computing bearing strength.

Sec. 34. Thickness.—Faced walls shall be not less in thicknessthan is required for masonry walls of the type which forms thebacking. Where bonded to the backing as provided in section 35the facing may be considered a part of the wall thickness.

Sec. 35. Bond.—Brick facing shall be bonded to walls of brick orof hollow tile, or of concrete block or tile with at least one header

course in every six courses, or there shall be at least one full length

header in every 72 square inches of wall surface.

Stone ashlar facing shall have at least 20 per cent of the super-

ficial area not less than 3% inches thicker than the remainder of thefacing to form bond stones, which shall be uniformly distributedthroughout the wall.

When some stone in every alternate course are at least 7% inchesthick, bonded into the backing at least 3% inches, and at least 20per cent of the superficial area of the wall is constituted of such

bond stone uniformly distributed, the ashlar facing may be countedas part of the wall thickness. Every stone not a bond stone andevery projecting stone shall be securely anchored to the backing with

substantial noncorrodible metal anchors. (See Appendix, par. 32-8.)

ARTICLE VIII.—FIRE WALLS, FIRE DIVISION WALLS, ANDPARTITIONS

Sec. 36. Brick and Plain Concrete Fire Walls.—Solid brick orplain concrete fire walls shall be not less in thickness than required

for exterior bearing walls of corresponding height, but not less than

12 inches, except that solid brick fire walls for buildings of residen-

tial occupancy shall be not less than 8 inches thick for the uppermost

20 feet of height and shall be at least 12 inches thick for the remain-

ing lower portion;and except that plain concrete fire walls for such

structures may be 8 inches throughout. No 8-inch fire wall shall bebroken into, subsequent to building, for the insertion of structural

members. (See Appendix, par. 7-6, -8, and -9, and par. 17. Fordefinitions of fire and fire division walls, see Part II, sec. 1.)Party walls which function also as fire walls shall conform to re-

quirements for fire walls.


A separation of at least 4 inches of solid masonry shall be pro-vided in all fire and party walls between combustible members whichmay enter such walls from opposite sides.

Sec. 37. Fire Walls of Hollow Tile, Concrete Block or Con-crete Tile, or of Hollow Wall Construction.—Fire walls of hol-low tile or concrete block or concrete tile shall be not less than 16

inches thick in any part, except that for residental buildings they

may be not less than 12 inches thick throughout. Hollow walls ofbrick used as fire walls shall be not less than 12 inches thick through-

out. No fire walls of the above types shall be broken into, subse-quent to erection, for the insertion of structural members. (See Ap-2iendix, par. 7-5 and -6, and par. 17.)Where combustible or unprotected steel building members frame

into hollow party or fire walls of thickness not greater than 12

inches, they shall not project more than 4 inches into the wall and

shall be so spaced that the distance between embedded ends is notless than 4 inches. The space above, below, and between them shallbe filled solidly with burnt-clay materials, mortar, concrete, or

equivalent fire-resistive material, to a depth of not less than 4 inches

on all sides of the members.All open cells in tile or blocks occurring at wall ends shall be

filled solid with concrete for at least a depth of 6 inches, or closure

tile set in the opposite direction shall be used.

Party walls which function also as fire walls shall conform to

requirements for fire walls.

Sec. 38. Fire Division Walls.

—

Fire division walls of solid brick

or plain concrete shall be not less than 8 inches thick.

Fire division walls of hollow tile, or of concrete block or tile,

shall be not less than 12 inches thick in any part, and for buildings

of storage and heavy manufacturing occupancy they shall be notless than 16 inches thick throughout. Hollow walls of brick usedas fire division walls shall be not less than 12 inches thick through-

out. (See Appendix, pars. 7 and 17.)

Sec. 39. Alternate Requirements for Fire and Fire DivisionWalls.—Wall constructions that in fire tests conducted according toaccepted standards develop safe fire-resistance periods of one andone-half hours may be permitted for fire walls and fire divisionwalls between residence occupancies, if otherwise adequate in point

of strength and stability. For general mercantile and manufactur-ing occupancies, excluding buildings or portions of buildings used

for storage, wall constructions developing, on the same basis, a safefire-resistance period of three hours shall be similarly permitted.

Note.—For requirements for lateral support of walls, see Part II, sections3, 10, and 18.

28934°—25 4


Sec. 40. Parapet Walls.—In commercial or industrial buildingsand in residential buildings over three stories high, all fire or party-walls shall project above the roof as parapets.

Where not otherwise specified parapet walls shall be at least 32inches high, but not higher than four times their thickness unless

laterally supported. They shall be at least as thick as the top storywall, except that they need not in any case be more than 12 inchesthick.

In residential buildings not more than three stories high parapetwalls shall extend through combustible roofs to a height of at least

12 inches above the roof. All parapet walls shall be coped. (See

Appendix, par. 29.)Sec. 41. Bearing Partitions.

—

All interior bearing walls, except

fire walls, fire division walls, and party walls, are considered as bear-

ing partitions.

For bearing partitions, materials meeting the ordinary acceptedlocal standards for the purpose may be used.Where not utilized as party, fire, or fire division walls solid brick

bearing partitions shall be not less than 8 inches thick, and those ofhollow tile, concrete block or concrete tile, or hollow walls of brick

shall be not less in thickness than one-eighteenth of the height be-

tween floors or floor beams. (For conditions governing concentra-

tions see sec. 4.)

Sec. 42. Nonbearing Partitions.—For nonbearing partitions, ma-terials meeting the ordinary accepted local standards for the purpose

may be used.Brick nonbearing partitions shall be not less than 3% inches thick

for a height not exceeding 12 feet between floors or floor beams andfor a length not exceeding 20 feet between vertical supports. Non-bearing partitions of hollow tile, concrete block or concrete tile,,

hollow walls of brick or of gypsum block or other similar materialsshall be built solidly against floor and ceiling construction below andabove, and shall not exceed the following unsupported heights

:

Thicknessexclusiveofplaster

Maximumunsupported

height

Thicknessexclusiveof plaster

Maximumunsupported

height

Inches Feet Inches Feet2 6 203 12 8 254 15

ARTICLE IX.—FOUNDATION WALLS

Seo. 43. Foundation Walls.

—

Foundation walls for solid-wall

construction shall be of stone, solid brick, concrete (plain, rubble,,

or reinforced), or concrete block. Solid brick foundation walls


and those of concrete block or coursed stone shall be not less inthickness than the walls immediately above them and in no caseless than 12 inches thick, except that when the inclosure is not ex-cavated, they may be 8 inches thick if included within the allow-able height of 8-inch walls. When built of concrete cast in place,foundation walls shall be at least as thick as the walls supported,

but in no case less than 8 inches. When built of rubble stone, theyshall be at least 16 inches thick. Rough or random rubble withoutbonding or level beds shall not be used as foundations for walls

exceeding 35 feet in height nor shall coursed bonded rubble walls

be used as foundations for walls exceeding 75 feet in height. (See

Appendix, par. 18-1.)

Foundation walls for hollow tile, concrete block or tile, hollow

walls of brick, or frame construction, shall be of the same thick-

nesses, respectively, as required in the paragraph above, and shall

be built of brick, stone, concrete (plain, rubble, or reinforced), hol-

low tile, concrete block or tile, or hollow walls of brick. Tile foun-

dation walls shall be not less than 12 inches thick.

When the stresses due to earth pressure and superposed buildingload exceed the maximum working stress elsewhere specified forbrick masonry, and the additional stresses are not otherwise pro-

vided for, the wall thickness shall be increased to bring them with-

in these limits. (See Appendix, par. 30.)Foundation walls for frame construction shall extend at least 8

inches above the adjoining ground surface.

All foundation walls shall extend below the level of frost ac-

tion.

Materials for foundation walls shall be equal in quality in all

respects to those required for exterior bearing walls, except that

mortar containing lime in greater proportions by volume than 1

part to 1 part of cement and 6 parts of sand shall not be used for

exterior foundation walls below grade. (See Appendix, par. 30-2.)

ARTICLE X.—SKELETON CONSTRUCTION

Sec. 44. Panel and Inclosure Walls.—Panel walls in buildingsof skeleton construction shall be not less than 8 inches thick if

of solid brick, hollow tile, concrete block or tile, plain concrete,

or hollow walls of brick. Inclosure walls shall be not less than 8

inches thick nor less in thickness than one-twentieth the horizontal

distance between anchors. (See Appendix, par. 6-2.)

ARTICLE XI.—NEW TYPES OF MASONRY CONSTRUCTION

Sec. 45. New Masonry Construction.—The use of new or im-proved masonry materials or methods not covered by this code may


be permitted, providing that they conform to specifications insur-ing reasonable uniformity of the product; and that the stabilityand durability of such construction, and its resistance under fireexposure shall have been satisfactorily demonstrated. Workingstresses shall be fixed at not more than 20 per cent of the averageultimate strength of masonry walls constructed of such materials,as determined by responsible authorities. (See Appendix, par. 31.)

ARTICLE XII.—MISCELLANEOUS REQUIREMENTS

Sec. 46. Anchoring Walls.

—

All walls shall be securely anchored

and bonded at points where they intersect. (See Appendix, par.

32.)

Sec. 47. Use of Existing Walls.

—

An existing brick wall may beused in the renewal or extension of a building; or may be increasedin height beyond that allowed by this code for walls of its existingthickness and materials of construction, provided that such wall isstructurally sound or can be made so by reasonable repairs. Wallsincreased in height shall be at least 4 inches thicker than is re-

quired by this code for newly constructed walls of such increasedheight, and in no case shall linings be less than 8 inches thick andlaid in Portland cement mortar. The foundations and lateral sup-port shall be equivalent to those elsewhere required for newly con-

structed walls under similar conditions. All linings shall be thor-

oughly bonded into existing masonry by toothings of brick or stoneto assure combined action of wall and lining. Such toothings shallbe distributed fairly uniformly throughout the wall and shall ag-gregate in vertical cross-sectional area not less than 15 per cent of

the total vertical area of the lining. (See Appendix, pars. 22 and

32-1.)

No existing wall shall be used for renewal or extension of a build-ing, or increased in height without special written permission from

the building official.

Sec. 48. Corbeling of Chimneys.—No brick wall less than 12inches thick shall be used to support a corbeled chimney. Such

corbeling shall not project more than 6 inches from the face of the

wall, and in all such cases the corbeling shall consist of at least

five courses of brick. No chimney shall be corbeled from a wallbuilt of hollow tile, hollow concrete block, concrete tile, or hollow

walls of brick.

Sec. 49. Cornices.—The centers of gravity of stone cornices shallbe inside of the outer wall face. Terra cotta or metal cornices shall

be structurally supported from the roof of the building.

PART III.—APPENDIX

PARAGRAPH i. PURPOSE

The Appendix consists of explanatory matter referring to PartII and is a vital part of this report. The committee believes thatevery building code should be accompanied by an appendix whichshould contain sufficient explanation of the code requirements tomake them easily understandable and such other information ongood practice as is not easily obtainable elsewhere in concise form.

PARAGRAPH 2. JUSTIFICATION FOR REQUIREMENTS, AND INFLU-ENCE OF BUILDING INSPECTION

1. It is recognized that the requirements recommended in Part IIconstitute in some particulars relaxations from those in force in cer-tain cities and parts of the country. These modifications of existingpractice are justified by the facts developed through the committee’sinvestigations. In addition to the test data discussed in the follow-ing pages the experience has been noted of several large cities whichfor many years have utilized wall heights, thicknesses, and stresslimits fully as liberal as those recommended in Part II. The suc-cess resulting with these moderate requirements in many places andunder varied circumstances is the most satisfactory answer to theobjections to their adoption in localities where present requirementsare more conservative.The recommendations are 'predicated on the assumption that good

materials and workmanship will be used and all necessary care takenin assembling the various parts of the structure. Certain existingcode provisions applying to walls and other structural details, whichmight be classified as extreme, reflect in part the purpose of theirwriters to offset poor design or workmanship by a greater factor ofsafety. In effect such codes penalize the builder, by requiring addi-tional material and labor because of a city’s failure to provide, orcompel the provision of adequate and competent supervision ofbuilding operations. It is felt that the extra expense thus causedmore than warrants energetic measures to insure such supervision,and that it is the duty of all concerned with planning and super-vising building construction, both to the public and to their clients,to use every influence toward securing it.

2. Where responsible supervision can be assured the code require-ments recommended in this report are believed safe. Where inspec-tion is of uncertain character relaxation of more restrictive or ex-pensive existing requirements is not advocated. In modifying theircode provisions to reduce cost, local authorities should insist uponsupervision of construction by an adequate experienced personnel.At the same time, city building inspectors should avoid the other

extreme. There is a tendency for the building inspection depart-ments of municipalities to forget that theirs is primarily a policefunction, concerned only with public safety, and to lay too muchstress on matters which are good building practice, but have nothingto do with the police power. This is reflected to a considerableextent in some recent building codes, and in preparing these recom-mendations the effort has been made to keep them within the boundsof simplicity necessitated by safety considerations alone.

21


3. The committee for the most part has confined itself to structuralrequirements and has avoided matters of administration. The pub-lic discussion of the tentative report, however, discloses a strongsentiment for placing greater responsibility on those charged withbuilding construction, and a few remarks on this subject seemdesirable.

The municipal building inspector is not and should not be heldwholly responsible for safety of buildings. His duty, like that ofthe policeman, is to prevent dangerous conditions, so far as hisfacilities will permit, but reasonable precautions having been taken,he is no more responsible for failures than the policeman for crimes.The builder or his accredited representative, having undertakenerection of the structure, is responsible for safe prosecution of thework. Building erection, especially of the large structures nowprevalent, is an operation of great complexity involving numerouspossibilities of mishap, both to those engaged in the work and tofuture occupants. The risks involved and the knowledge demandedof those in charge are far greater than in the case of many tradesor occupations now rigidly controlled. Nevertheless, such work isfrequently undertaken by those having practically no experienceand often assuming an antagonistic attitude toward the buildinginspector’s efforts to insure safety.

In view of these facts some discretion should be accorded buildingofficials as to who may be granted permits. The committee does notnecessarily advocate licensing of builders, but does hold that localpractice should strongly favor the issuance of permits only toresponsible individuals experienced in building work and competentto assume responsibility for their employees and subcontractors;and that building officials should be empowered to refuse permits tothose known to be unfit for the work proposed or who have failedformerly to cooperate sufficiently with municipal inspection to insurereasonable safety. This means that permits would be issued onlyto the builder, architect, or person who is responsible for erection ofthe building, and not necessarily to the owner.

PARAGRAPH 3. STATUS OF THE COMMITTEE’S RECOMMENDATIONS

1. It has been called to the committee’s attention that some mis-understanding exists regarding the legal status of its recommenda-tions. It should be recognized that the committee’s functions arepurely advisory. Its recommendations can not be considered in anysense as obligatory, but are issued to make available to those locallyresponsible for exercise of the police power the latest and mostreliable information obtainable on building regulations.

2. The recommended code requirements are in all cases the mini-mum consistent with safety predicated upon proper design andgood workmanship. The scope of the police power, upon whichall such ordinances depend for authority, does not justify require-ments which are merely good building practice, and where suchrequirements are included in codes they are apt to be found unen-forceable.

When two or more materials or methods of construction are men-tioned in this report as satisfying a certain requirement, it does notfollow that they are considered on a par in all desirable respects,

APPENDIX 23

but merely that they meet the standards of performance regardedas essential.

3. It is not intended that these recommendations shall be regardedas fixed. Building laws can continue to be of the highest usefulnessonly when they reflect progress in the art of building construction.Many of the injustices and discrepancies of existing building codesresult from delay in their revision to meet changing conditions. It isplanned that these recommendations shall be amended at intervals,keeping pace with changes in building art. In this way it is hopedthat best assistance may be rendered those responsible for revisionand enforcement of building ordinances.

PARAGRAPH 4. FUNCTION OF WALLS

Under prevailing interpretations of the police power there arecertain definite requirements which masonry walls in buildings mustmeet.

1. They must not fail structurally under loads or conditions in-cidental to the building’s occupancy.

2. They must resist moisture penetration to an extent which willinsure sanitary living or working conditions, and the permanency ofthe wall itself or of members framing into it.

3. Under fire exposure their stability must be such as to avoidpremature collapse endangering firemen, and they must dischargethe functions of support and heat insulation, necessary to preventundue fire loss.4

PARAGRAPH 5. VARIATION IN CODE REQUIREMENTS

So far as can be determined from an examination of presentmunicipal regulations, experience in satisfying these requirementshas not resulted in uniform practice. The committee had referenceto four independent investigations on this subject.

1. An analysis by the Bureau of Standards of the requirements of134 building codes, representing all parts of the country, disclosedthe following facts.

Average requirements and limitation's of 13Jf codes for brick foundations andsolid exterior walls for dwellings

THICKNESS WITHIN FIRE LIMITS ONLY

Foundation,in inches

Stories Limits of

First Second Third Fourth Height Length Width Area

12.5

Inches9.7

11.013.116.0

Inches Inches Inches Feet15.528.741.553.7

Feet65.969.880.280.6

Feet23.724.324.4

Si. ft.1, 311

1, 31113 7 9.711.813.6

16.2 10.512.318.5 — 11.2 24.9

THICKNESS WITHIN OR OUTSIDE OF FIRE LIMITS

12.5

13.6

16.218.5

). 2

12.814.4

15.

9.211.5 10. 213.2 12.0 11.0

28.541.554.0

* The protection of stored, commodities or prevention of interior deterioration is alsoan important function of walls and should be considered. It does not come within thepolice power.


Among the 134 codes there were 3 different minimum thicknessesprescribed for one-story residential buildings, 4 for two-story dwell-

ings, 8 for three-story dwellings, and no less than 12 different mini-mum thickness arrangements allowable for the different stories offour-story buildings. Other conditions being equal the thickest four-story wall contained 125 per cent more brick than the thinnest. Asimilar situation was found to exit in regard to walls of hollow tileand hollow concrete block.

2. A compilation by the Common Brick Manufacturers’ Associa-tion of America of the allowable thicknesses of solid brick exteriorwalls of dwellings as given in 113 building codes and summarized asfollows

:

Minimum, allowable thickness of solid, brick exterior walls for dwellings accord-ing to building codes of 113 cities

Dwellings Walls Cities

One-story 8-inch.. 88Do Over 8-inch 25

Two-story 8-inch, both stories 44Do Over 8-inch, first story 38Do Over 8-inch, both stories 31

Three-story 8-inch, all storiesDo Over 8-inch, first story 17Do Over 8-inch, first and second stories 30Do Over 8-inch, all stories 53

3. An investigation was made by the committee of code require-ments for panel walls supported at each story, with the followingresults

:

Of 84 municipal building codes examined, 30 do not distinguishbetween panel walls supported at every story and bearing walls ornonbearing walls not thus supported.

Six codes recognize panel walls as a separate class, but requirethat their thickness for the lower stories be increased with theheight of the building in the same manner as for walls not thussupported.

Forty-eight ordinances specify minimum allowable thicknesses forbrick panel walls : Of these, 18 call for 8-inch thickness, and 30 callfor 12 or 13 inch thickness in such walls.

Thirty-three codes specify thicknesses for tile panel walls as fol-lows: 14 require 8-inch thickness, and 19 call for 12 or 13 inchthickness.

In 39 cases specific requirements for thickness of reinforced con-crete panel walls are given, namely: 2 require 4-inch thickness, 4require 6-inch thickness, 16 require 8-inch thickness, 12 require 12-

inch or 13-inch thicknesses.Only one code specifically mentions the use of concrete units for

panel walls, the thickness required being 12 inches.Fourteen codes make no difference between the various masonry

materials, merely stating the thickness. Of these, six call for an8-inch wall and eight call for a 12-inch wall.Two codes forbid such walls to be thinner than one-sixteenth or

one-twentieth of their height between horizontal supports.

APPENDIX 25

One code specifies that panel walls shall not be longer than 20feet between vertical supports, but does not limit their height.Nine codes limit the height between horizontal supports, requir-

ing that the thickness be increased if the limits are exceeded. Theselimits vary between 10 and 20 feet. In some cases they apply tospecific materials only and in other cases their application appar-ently is general.

Ten codes limit both height and length of panel walls supportedat each story, the limits varying from 12 by 12 feet to 14 by 30 feet.In most cases the larger limits are for the thinnest walls.Two codes regulate thickness on basis of square feet of wall

surface.

Three codes require party wall panels to be 4 inches thicker thanexterior walls.

Omitting from consideration the codes which require increasedthickness with increasing height of building, the average of thepanel wall thicknesses specified in the 84 codes was 10.86 inches forbrick, 10 inches for hollow tile, and 8.57 inches for reinforcedconcrete.

4. An analysis of requirements regarding necessary thickness ofbrick bearing walls for eight-story structures in 20 codes chosen atrandom disclosed 18 different sets of requirements, and doubtlessfurther investigation would have discovered others. These varia-tions, furthermore, bore no particular relation to requirements gov-erning other factors which should affect the wall thickness.

Variation, such as demonstrated above, arises in part from thefact that standards of performance are unequal; that exposuresand allowable working stresses vary; and that materials and work-manship differ widely in different localities. It also is due in verylarge measure to local custom, unchecked by adequate knowledgeof construction practice elsewhere, and to slavish copying of otherordinances without due regard for the circumstances attending theiradoption. In theory, at least, minimum standards of performanceshould be uniform, irrespective of location and other conditions,except, perhaps, those due to climate, and when departure is madefrom minimum standards scientifically determined the reasons forsuch departure should be carefully considered.

Part II of this report presents all the requirements which theBuilding Code Committee considers essential to meet such uniformstandards of performance, and states these recommended require-ments in the minimum terms considered necessary for protection ofthe public health and safety.

PARAGRAPH 6. WALLS IN SKELETON CONSTRUCTION

1. In skeleton construction that portion of a panel wall betweenwindow sill and floor is sometimes called an apron wall. The por-tion between the window top and the floor construction above isoccasionally designated as a spandrel wall.

2. In view of some confusion which exists in use of the terms“ panel wall ” and “ curtain wall,” their definition in a code is con-

289340—25 5


sidered necessary. Inclosure walls, as defined in Part II, section 1,refer only to nonbearing walls inclosing a structure, but not neces-sarily built between columns or piers and only sufficiently anchoredto them or to floors to insure stability against lateral forces. Theymay be supported at each story or at intervals of two or more stories,as best suits the design.

3. Several critics of the tentative draft of this report suggestedthat the definition of “ panel wall ” be expanded to include those sup-ported at every second or third floor line, or at intervals of 20 or 30feet. It was evident, however, that several of these criticisms re-ferred to a, somewhat different method of construction. The com-mittee has included these other types of walls under the term “ in-closure walls.”

4. The tentative draft of this report permitted the use of metalfabric and cement plaster, or “ gunite ” walls. The consensus ofopinion obtained indicated that such walls do not properly belongunder the heading of masonry. The committee, therefore, hasomitted them.

5. Some existing codes regulate the thickness of walls in skeletonconstruction according to the length, height, or area in square feetbetween columns and floors. If the limitations on spacing of lateralsupports recommended in Part II are observed, this will be unneces-sary. It is established, in fact, that the expansion of such walls underintense heat is less destructive, and the deformations are less, ifthe panels are long, than if they approach a square in shape.

PARAGRAPH 7. FIRE AND FIRE DIVISION WALLS

1. In order adequately to discharge its functions, a fire wall mustbe thick enough to prevent communication of fire by heat conduction.It must have such stability as to remain intact after complete com-bustion of the contents of the building on one side of the wall

;and

its structural integrity must be such as to be not seriously affected byany wreckage resulting from the fire or its extinguishment.

2. It is no longer customary in steel and reinforced concrete con-struction to build self-supporting fire walls up through a structureindependently of the floors, even though such walls are sometimesspecified in codes. The walls are supported by the structural frameor floor system in each story, and usually divided into moderatelysmall panels built between piers or columns. In case of fire, thismethod of restrained construction serves to limit the heat deformationin a single unit to an amount which does not endanger the integrityof the wall. Such walls are termed “ fire division walls ” in this re-port to distinguish them from the walls commonly known as “firewalls.”

3. Exhaustive tests under severe conditions at the Bureau of Stand-ards indicate that well-built 8-inch solid brick walls supported ateach story with no combustible members framing into them are re-liable as fire stops, and that so long as the floor and roof constructionmaintain their integrity, a safe fire barrier exists between buildingsor parts of buildings separated by such walls. (See also Appendix,par. 17.)

APPENDIX 27

4. The type of wall defined in Part II, section 1, as a “ fire wall ” isthe result of experience antedating successful fire resistive skeletonconstruction. Walls of considerable mass and stability, extendingunbroken from foundations to parapet, were and are necessary in“ ordinary ” and “ mill construction,” where floors can not be de-pended upon to resist the full duration of a fire and are liable tocollapse, or where beams and girders depend on such walls forsupport. The modem method of skeleton construction providesfloors, girders, and columns which support the walls and partitionsinstead of being supported by them.Experienced observers hold that high independent fire walls be-

tween buildings or parts of a building of ordinary construction areas apt to fail in event of a severe fire as the floors or roofs of well-builtfire-resistive skeleton structures, even though the fire walls conformto the usual rigid requirements. Consequently the panel wall be-tween floors in buildings of fire-resistive skeleton construction is anadequate alternative for the old type of fire wall.With these considerations in mind the committee has provided for

two types of fire-resistive walls, the first corresponding to existingstandards, to be required for “ mill construction ” buildings andthose of “ ordinary ” or wood joist construction; the second to be per-mitted wherever fire barriers are necessary within or between build-ings of skeleton construction. (See also Appendix, par. 17.)To prevent a fire lapping around the ends of a fire wall or fire

division wall the committee recommends that no openings be per-mitted in the exterior walls of a building within five feet of theirintersection with fire walls. For the same reason, fire walls in frameconstruction should be built with wings at each end where theyintersect the exterior walls. Such wings should be the full heightof the fire wall and extend at least five feet on each side of the firewall in the plane of the exterior wall.

5. The requirements of Part II for hollow fire and fire divisionwalls, or those of hollow units, recognize the possibility of theirremaining unplastered. Such walls usually are plastered and anextra element of safety is thus introduced, as observation of suchwalls under fire exposure discloses that plaster applied to bothsurfaces is of considerable value in delaying transmission of dan-gerous temperatures and in preventing damage to the units. Plasteralso adds to the stability of thin tile walls, though not in proportionto the additional thickness. Its use on tile and concrete-block wallsis strongly advocated, especially in the case of party and fire walls.

6. The intent of Part II, section 36, is that no attempt shall bemade to break into an 8-inch party wall for insertion of buildingmembers, subsequent to its erection. It was felt that if joists or othertimbers were installed at the time of erection with ends staggered andthe masonry joints between them carefully filled with mortar, suchminimum thickness might be safely employed. Where members areinserted subsequently, it is very difficult to be sure that joist ends areproperly staggered and that no dangerous crevices are left in the wallat the floor line. A similar but more drastic requirement was madefor walls of hollow units because of the greater danger that breakageof such units will open communication between opposite sides ofthe walL


7. The requirements of Part II, section 36, permit the uppermost20 feet of a fire wall in a building for residential purposes to be 8inches thick with joists inserted. This, of course, does not meanthat such walls will occur in the upper stories of high buildings, forcodes do not, in general, permit the use of joisted or mill constructionin buildings over five stories in height. Exterior walls receive sup-port from but one direction and the use of 8-inch thickness, therefore,was limited to the top stories of buildings not over three stories high,with further restrictions as to support and roof framing. (SeePart II, sec. 5.)

8. Kequirements for control of fire-wall openings are not con-sidered within the scope of this report.

9. The suitability of lime mortar for fire and fire division wallshas been questioned, but there appear to be no positive data indicat-ing that it is unsafe for solid brick walls. Hollow walls or those ofhollow units are required to be laid with cement or cement-limemortar, whether or not functioning as fire walls. (See Part II,sec. 9.) (See also Appendix, par. 17-2, for discussion of mortars infire walls.)

PARAGRAPH 8. CONCRETE CONSIDERED AS MASONRY

1. Strictly speaking the term “ masonry ” is limited to the use ofstone units. In the early history of building trades, a mason was aworkman who dealt with stone work only. A mason, which alsoimplied stonecutter, was a somewhat different type of mechanicthan he who now builds with brick and tile. These terms, togetherwith that of plasterer, have come down to us from the ancient guilds,but have gained recently a more general application.

2. Modern practice has developed the wall of mass concrete, andthat of rough stone grouted with mortar, having the same functionsand general requirements as masonry of the older types. It wasdecided that these should be termed masonry and treated in the samereport with walls laid up with masonry units.

3. Walls of reinforced concrete owe their strength and stabilitylargely to factors other than those governing masonry walls andtherefore have been omitted from the scope of this report.

PARAGRAPH 9. QUALITY OF BRICK

1. The requirements of many building codes date from a time whenburned clay units were practically the only materials classed as brick.In order to prevent any misunderstanding of its recommendations,therefore, the committee believes it best to point out specifically asin Part II, section 1, note 2, that for the purposes of this report,unless otherwise stated, units of other materials having the samegeneral shape and size as brick are included with those of clay, itbeing understood that all units shall meet the test specificationsprovided herein.

2. The Building Code Committee has adopted the standard specifi-cation of the American Society for Testing Materials for mediumbrick as the basis of a minimum requirement for clay and sand-lime

APPENDIX 29

building brick used in load-bearing masonry. On account of prac-tical code enforcement difficulties, no provision has been made forrecognition of several grades of building brick as described in thesociety’s standard specification. It is reported, however, that severallocalities are using successfully a thoroughly burned brick with highcompressive strength and absorption considerably exceeding theAmerican Society for Testing Materials limits for “ medium ” brick.No undesirable weathering of such brick is reported, though used insome cases under extremely adverse conditions, and the 2,500 poundalternative requirement, therefore, has been inserted to permit theiruse.

Where a particular make of brick has been in general local usefor a period of years and has shown satisfactory service and weatherresistance

;or where such brick have demonstrated satisfactory

durability when tested by not less than 100 alternate freezings andthawings, or where climatic conditions make absorption limits unim-portant, the absorption requirements may be waived for all ordinarypurposes, subject to supervision by the building officials havingjurisdiction.

Where it is established to the satisfaction of those in authoritythat the quality of brick available for load-bearing masonry is uni-formly higher in compressive and transverse strength than themedium grade described by the American Society for Testing Mate-rials standard, it is recommended that reasonable increases based oncompressive strength of the units, be allowed in the unit workingstresses recommended in Part II, section 4.The use of so-called “hollow brick” also should be permitted if

they meet the requirements of Part II, section 2.The following classification of brick is taken from the Standard

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